Challenge
Jobs that are using a proxy, windows repository, or Hyper-V host that have multiple NICs are failing with “Error: Completion Timeout Occurred”
Cause
Unless the preferred network is specified, by default Veeam will attempt to establish a connection with each NIC on the target host and then automatically determine which one it should use. When there are multiple NICs and connectivity is only possible to some of them, sometimes the agent will retry establishing connections on the other NICs until it times out.
Solution
For each server that has multiple NICs, please set the preferred network to be used for the backup traffic. This option can be found in the menu button under “Network Traffic > Networks…”, and is described here in our userguide: http://helpcenter.veeam.com/backup/80/vsphere/index.html?select_backup_network.html
More Information
The IP connection timeout itself can also be increased by adding the following registry key to HKey_local_machine\software\Veeam\veeam backup and replication\
ConnectByIPsTimeoutSec
Type: REG_DWORD
value: 1200